Sheet grader

ABSTRACT

Apparatus for grading sheets such as plywood veneers, according to size in which the sheets are conveyed past a suction head which has two ducts and a channel between them, the ducts being spaced apart in the direction of travel of the sheets. The arrangement is such that oversized sheets cover, at all times while beneath the grader, at least a part of one of the ducts whereas undersize sheets can be covering only the channel so that the oversize sheets are conveyed past the grader while the undersize sheets fall from it.

lnventor Victor Prochaska ll-llaus No. 103, Austria Appl. No. 14,929 Filed Feb. 27, 1970 Patented Nov. 23, 1971 Assignee Durand Machine Company Ltd. New Westminster, B.C., Canada SHEET GRADER 9 Claims, 3 Drawing Figs.

11.8. CI 209/82, 271/74 lnLCl. 1. B071) 13/04 Weld oih 209/74, 82; 271/74 {56] References Cited UNlTED STATES PATENTS 3,476,241 ll/1969 Ungerer 271/74 X 3,490,764 1/1970 Muller et al. 271/74 Primary ExaminerRichard A. Schacher Assislanl ExaminerGene A, Church Altorrzey-Fetherstonhaugh & Co.

ABSTRACT: Apparatus for grading sheets such as plywood veneers, according to size in which the sheets are conveyed past a suction head which has two ducts and a channel between them, the ducts being spaced apart in the direction of travel of the sheets. The arrangement is such that oversized sheets cover, at all times while beneath the grader, at least a part of one of the ducts whereas undersize sheets can be covering only the channel so that the oversize sheets are conveyed past the grader while the undersize sheets fall from it.

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sum 2 or 2 mvem'on VICTOR PRQCHASKA AT I'O 2Y5 SHEET GRADER This invention is concerned with apparatus for grading sheets into those above and those below a certain size. It is particularly but not necessarily exclusively, concerned with apparatus for grading plywood veneers.

The invention is concerned with an apparatus in which the grading is made as the sheets travel along a conveyor and the expression size" as used herein relates to the dimensions of the sheet in the direction of their travel along the conveyor.

A known method of grading veneers by size is one in which the veneers are conveyed past photocells set to the size required of the veneers and which control a solenoid valve which operates a pneumatic piston and'cylinder which causes a kicker mechanism to move into the path of the veneers on the conveyor and to divert those veneers from the conveyor.

This sort of arrangement is cumbersome and requires-considerable maintenance for the constantly operating valves and piston and cylinder units.

SUMMARY OF THE INVENTION This invention seeks to provide an alternative and simpler grader. According to this invention there is provided a grader having a suction head with two downwardly directed inlets spaced apart in the direction of travel of the sheet to be graded, the spacing of the inlets being related to the size to either side in which it is required to grade the sheets, the two inlets being interconnected by a shallow, downwardly open channel which extends in the direction of travel and means for moving the sheets over the inlets and channel, the arrangement being such that an oversized panel is maintained against the suction head'whereas an undersized panel will fall from it.

From another aspect there is provided according to this invention, a grader 'comprisinga conveyor and a pair of ducts opening downwardly towards the conveyor and to which vacuum maybe applied to hold sheets to be graded against the underside of the conveyor by suction, the ducts being spaced apart in the direction of travel of the conveyor and being interconnected by a channel, the ducts being so spaced that sheets above a certain size are held onto the conveyor by suction and those below that size will fall from it.

Generally speaking the ducts will be so spaced apart that a sheet above the size to either side of which it is required to grade the sheets, located with its center midway between the ducts, will cover at leasta part of each of the downwardly opening inlets of the ducts and with an undersized sheet so located, no parts of the openings would be covered. ln other words the space between the closest edges of the openings is approximately equal to the size to either side of which the sheets are I to be graded. However, dependent upon the vacuum created at the inlets, and the weight and speed of travel of thesheets, the distance between adjacentedges of the openings may be greater or smaller than the said size.

For easyreference throughout'this specification the size to either side of which the sheets to be graded will refer to as the size" orsize as the context permits. Sheets above that size will be referred to as oversize" sheets and sheets below that size will be referred to as undersize" sheets,

It is to be appreciated size.with irregular sheets as for example plywood veneers the definition between under and oversized sheets or the precision 'with which th'edevice may operate, is limited. In such cases it is desirable to arrange that the grader divide the sheets to be graded into those slightly below size" and over size and into those noticeably below size." In this way the grader is passing all sheets over size" but is rejecting (or allowing to fall) those noticeably below size. To make the more precise definition often required it is convenient to provide some separate device toknock the sheets which are below but only slightly below, size" from the conveyor. Such a device may be a pneumatic piston and cylinder unit controlled by a solenoid valve which is actuated by size sensing means such as for example spaced microswitches or photocells. The sensing means would be spaced apart in the direction of travel of the sheets or veneers a distance equal to size" and arranged only to operate when a sheet which would be passed by the vacuum grader but is slightly below size" is passed along the conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS grader according to this inven- DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment of FIGS. 1 and 2 comprises a frame generally indicated at 10, conveyors ll, 12 and I3, and a grader generally indicated at 20. The frame canbe of any desired. construction but forms no part of theinventionand as such is not described in detail herein. It is to be appreciated that its purpose is simply that of support and the frame could take any of many forms. An infeed conveyor 1 I feeds to a conveyor l2 and sheets travelling along that conveyor are separated by the grader 20 into those which are undersized and which continue along the conveyor 12 and those which are oversized which are passed to conveyor 13.

The apparatusillustrated in FIG. I is particularly suited for the grading of'plywood veneers and the conveyor 13 include two or more endless V-belts l4 trained overpulleys on shaft 21 and which overlie the veneers on the lower portion of conveyor 13 and prevent them from sliding back .down the conveyor.

The grader comprises fans 22 and 23 which draw air from associated manifolds 24 and 25 respectively. This arrangement is seen more particularlyin FIG. 2 but of course. in that Figure only the fan 22 and its associated manifold 24 are visible.

The manifold 24extends transversely of the conveyors and has downwardlydirected ducts 26, 27 and 28. The manifold 25 has similar ducts only one of which, 29, can be seen in FIG. 1. The ducts 26 and 29 are interconnected at their open lower inlet ends by a shallow channel 30 as are ducts 27 and 28 with the corresponding ducts of the manifold 25, the channels interconnectingthose latter two pairs of ducts being indicated in FIG. 2 by the numerals 31 and 32. The ends of channel 30 are closed as M333 and 34 as are the corresponding ends of the channels 31 and 32 but where the volume of airdrawn by the fan is large leakage through the ends of the channel can be tolerated and the ends could be left open,

Extending transversely of the conveyors, 11 and 12 and parallel to themanifolds 24 and 25 are shafts 40 and 41 upon which there are journaled, one to each side of each of the channels 30, 31 and 32, Vbelt pulleys 42, 43, 44, 45, 46, and 47, and trained over those pulleys are V-belts 48, the lower runs ofwhich follow the course of the lower marginal edges of the downwardly directed channels 30, 31 and 32.

The device operates asfollows:

As a veneer passes along the conveyor 12 beneath the downwardly directed openings of the ducts 26, 27 and 28, it is lifted upwardly and into engagement with the V-belts 48 and is carried forward. As it moves over the downward inlet openings of the ducts air passes along the channels 30, 31, and

32 to maintain the veneer in contact with the belts. An over;

sized veneer will reach a position in which its leading end is partly covering or completely covering the downwardly open inlets of the duct 29 and the other ducts of manifold 25 whilst its trailing end still partially covers or completely covers the inlets of the ducts 26, 27, and 29 and in such cases the suction effect at the inlets and in the channels 30, 31 and 32 will be sufficient to maintain the veneer against the belts until it is passed to the conveyor 13 to continue for further grading or processing.

A veneer which is undersized will be maintained on the V- belts beneath the ducts and channels only until it clears ducts 26, 27 and 28 and has not yet reached the ducts of manifold 25 at which time the suction effect which will be very slight in the channels 30, 31 and 32 and will not be sufiicient to maintain the veneer against the V-belts and the veneer will fall to conveyor 12 i.e. it will be separated from those veneers which are passed to conveyor 13.

It is to be appreciated that the spacing of the downwardly opening inlets of the ducts of the manifold 24 from those of the manifold 25 will be related to the size to either side of which it is required to grade the sheets and generally will be approximately such that the spacing between the adjacent edges of the ducts on manifold 24 and those on manifold 25 is equal to size." However, depending upon the weight of the veneers and their speed of travel it may difier slightly from that size.

ln the alternative embodiment illustrated in FIG. 3 there is shown a device which has but a single fan 50, a single manifold 51, and a plurality of pairs of ducts 52 and 53 which are spaced apart along the manifold and transversely of the direction of travel of the veneers, the pairs of ducts forming a generally inverted V and each duct having a downwardly opening inlet. Extending between the openings of each pair of ducts there is a shallow channel 55 and in this case it is to be noted that the oversize sheets or veneers will continue in a horizontal plane past the grader whilst the undersized ones will fall to a downwardly inclined conveyor.

The operation of the grader of FIG. 3 insofar as the vacuum grading is concerned is substantially similar to that of the embodiment of FIGS. 1 and 2. However, because the grading which may be made by the vacuum sorter of irregular sheets or veneers is not so precise as may be required, the inlet openings of the ducts are spaced to allow the passage of oversized sheets or veneers and sheets or veneers which are slightly less than size. Those veneers which are only slightly less than size and which otherwise would be passed as size and oversize by the grader may be knocked from the grader by a separate knock-offdevice.

The knock-off device comprises a piston and cylinder unit 60 of which the piston rod 61 is adapted to be extended into the line of travel of the veneers along the V-belt drive so that the veneers striking the piston rods are diverted from the V- belts and onto the downwardly directed conveyor for the undersized sheets. The piston and cylinder unit is arranged to be operated in a generally known fashion by a solenoid valve which is controlled by a sizesensing system which is adapted to distinguish between oversize sheets or veneers and those sheets which are only slightly less than size, so that the knockoff or diverter mechanism is actuated only when a sheet or veneer which is only slightly undersize passes the grader i.e. only operates on those sheets which fall within the lower accuracy to which the sheets are graded by vacuum. The sensing can comprise spaced limit switches or photocells for example.

Whilst the embodiments of this invention which are being described with reference to the drawings are especially related to the grading of plywood veneers it is to be appreciated that the invention may well find application in other areas.

As an example of how the device may be modified the channel need not be physically connected to the ducts but may simply be located between and separate from the ducts so that as a sheet covers a part of one of the ducts and a part of the channel so air is drawn along the channel to that duct.

lclaim:

l. Grader apparatus for sheets comprising a conveyor, a pair of ducts having downwardly directed openings adjacent to the conveyor, said openings being spaced apart in the direction of travel of the conveyor, a downwardly open channel extending in the direction of travel of the conveyor and located between the duct openings, and means for inducing suction in the ducts tending to maintain maximum suction in the duct openings and lesser suction in the channel, said suction drawin sheets passin below the ducts and channel into contact wrt the undersi e of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.

2. Apparatus as claimed in claim 1 in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.

3. Grader apparatus as claimed in claim 1 in which said channel interconnects the openings of said pair of ducts.

4. Apparatus as claimed in claim 3, in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.

5. Grader apparatus as claimed in claim 1 including a mechanism operable to move into the path of sheets supported on the conveyor and to divert sheets from the conveyor, a control means associated with said mechanism and comprising size-detecting elements adapted to operate the mechanism to move it to its sheet-diverting position as a'sheet which has a length only slightly less than long enough to be subjected to maximum suction at both ducts at the same time, is against the conveyor.

6. Apparatus for grading sheets into those above and those below a certain size comprising a conveyor, a pair of ducts having inlet openings which are spaced apart along the conveyor a distance related to the size to either side of which it is required to grade the sheets, a channel opening towards the conveyor and interconnecting the inlet openings, and means for inducing suction in the ducts tending to maintain maximum suction in the duct openings and lesser suction in the channel, said suction-drawing sheets passing below the ducts and channel into contact with the underside of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is less than said size and not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.

7. Apparatus as claimed in claim 6 in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.

8. Apparatus for grading sheets according to size comprising a conveyor against the underside of which sheets to be graded can be supported by suction, a pair of ducts each having an inlet opening, the inlet openings being spaced apart along the conveyor and close to the conveyor and the ducts being connected to the low-pressure side of a fan, a channel interconnecting the inlet openings and opening downwardly towards and adjacent to the conveyor, said fan inducing maximum suction in the duct openings and lesser suction in the channel, said suction-drawing sheets passing below the ducts and channel into contact with the underside of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.

9. Apparatus as claimed in claim 8 in which there are at least two pairs of said ducts spaced apart transversely of the conveyor. 

1. Grader apparatus for sheets comprising a conveyor, a pair of ducts having downwardly directed openings adjacent to the conveyor, said openings being spaced apart in the direction of travel of the conveyor, a downwardly open channel extending in the direction of travel of the conveyor and located between the duct openings, and means for inducing suction in the ducts tending to maintain maximum suction in the duct openings and lesser suction in the channel, said suction drawing sheets passing below the ducts and channel into contact with the underside of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.
 2. Apparatus as claimed in claim 1 in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.
 3. Grader apparatus as claimed in claim 1 in which said channel interconnects the openings of said pair of ducts.
 4. Apparatus as claimed in claim 3, in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.
 5. Grader apparatus as claimed in claim 1 including a mechanism operable to move into the path of sheets supported on the conveyor and to divert sheets from the conveyor, a control means associated with said mechanism and comprising size-detecting elements adapted to operate the mechanism to move it to its sheet-diverting position as a sheet which has a length only slightly less than long enough to be subjected to maximum suction at both ducts at the same time, is against the conveyor.
 6. Apparatus for grading sheets into those above and those below a certain size comprising a conveyor, a pair of ducts having inlet openings which are spaced apart along the conveyor a distance related to the size to either side of which it is required to grade the sheets, a channel opening towards the conveyor and interconnecting the inlet openings, and means for inducing suction in the ducts tending to maintain maximum suction in the duct openings and lesser suction in the channel, said suction-drawing sheets passing below the ducts and channel into contact with the underside of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is less than said size and not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.
 7. Apparatus as claimed in claim 6 in which there are at least two pairs of said ducts spaced apart transversely of the conveyor.
 8. Apparatus for grading sheets according to size comprising a conveyor against the underside of which sheets to be graded can be supported by suction, a pair of ducts each having an inlet opening, the inlet openings being spaced apart along the conveyor and close to the conveyor and the ducts being connected to the low-pressure side of a fan, a channel interconnecting the inlet openings and opening downwardly towards and adjacent to the conveyor, said fan inducing maximum suction in the duct openings and lesser suction in the channel, said suction-drawing sheets passing below the ducts and channel into contact with the underside of the conveyor, and said lesser suction in the channel being insufficient to retain a sheet against the conveyor which is not long enough in said direction of travel to be subjected to substantially maximum suction at both ducts at the same time.
 9. Apparatus as claimed in claim
 8. in which there are at least two pairs of said ducts spaced apart transversely of the conveyor. 